# Top level methods and types

`CryoGrid.Algebraic`

— Type`Algebraic{name,S,T,units,domain} <: Var{name,S,T,units,domain}`

Defines an algebraic (implicit) state variable.

`CryoGrid.BCKind`

— Type`BCKind`

Trait that specifies the kind of boundary condition. This can be used to write generic implementations of `interact!`

that are (relatively) agnostic to specific implementations of `BoundaryProcess`

. A good example of this can be found in the `boundaryflux`

method interface.

`CryoGrid.BCKind`

— Method`BCKind(::Type{T})`

Can be overriden by `BoundaryProcess`

types to indicate the type of boundary condition, e.g:

`BCKind(::Type{BP}) = Dirichlet()`

where `BP`

is a `BoundaryProcess`

that provides the boundary conditions.

`CryoGrid.Bottom`

— Type`Bottom{TProc} <: Layer`

Generic "bottom" layer that marks the lower boundary of the subsurface grid.

`CryoGrid.BoundaryProcess`

— Type`BoundaryProcess{T<:SubSurfaceProcess}`

Abstract base type for boundary processes, i.e. processes that operate at the boundaries of the subsurface. A `BoundaryProcess`

represents the boundary conditions of one or more `SubSurfaceProcess`

es but may include its own diagnostic (or even prognostic) variables, if necessary.

`CryoGrid.CGEuler`

— Type`CGEuler <: SciMLBase.AbstractODEAlgorithm`

Simple, lightweight implementation of the forward Euler integration algorithm. Does not include support for fancier features such as interpolation, adaptive timestepping, or event handling. In order to get these features, you must install the `OrdinaryDiffEq`

package.

`CryoGrid.ConstantBC`

— Type`ConstantBC{P,S,T} <: BoundaryProcess{P}`

Constant boundary condition (of any type/unit) specified by `value`

.

`CryoGrid.Coupled2`

— Type`Coupled2{P1,P2} = CoupledProcesses{Tuple{T1,T2}} where {T1,T2}`

Type alias for coupled processes, i.e. `CoupledProcesses{Tuple{P1,P2}}`

. `Coupled`

provides a simple mechanism for defining new behaviors on multi-processes systems.

`CryoGrid.CoupledProcesses`

— Type`CoupledProcesses{TProcs} <: Process`

Represents an explicitly or implicitly coupled system of processes. `TProcs`

is always a `Tuple`

of other processes.

`CryoGrid.CryoGridProblem`

— Type`CryoGridProblem{iip,Tu,Tt,Tp,TT,Tsv,Tsf,Tcb,Tdf,Tkw} <: SciMLBase.AbstractODEProblem{Tu,Tt,iip}`

Represents a CryoGrid discretized PDE forward model configuration using the `SciMLBase`

/`DiffEqBase`

problem interface.

`CryoGrid.CryoGridProblem`

— Type```
CryoGridProblem(
tile::Tile,
u0::ComponentVector,
tspan::NTuple{2,Float64},
p=nothing;
saveat=3600.0,
savevars=(),
save_everystep=false,
save_start=true,
save_end=true,
step_limiter=timestep,
safety_factor=1,
max_step=true,
callback=nothing,
isoutofdomain=Tiles.domain(tile),
specialization=SciMLBase.AutoSpecialize,
function_kwargs=(),
prob_kwargs...
)
```

Constructor for `CryoGridProblem`

that automatically generates all necessary callbacks.

`CryoGrid.CryoGridProblem`

— Method`CryoGridProblem(tile::Tile, u0::ComponentVector, tspan::NTuple{2,DateTime}, args...;kwargs...)`

`CryoGrid.Diagnostic`

— Type`Diagnostic{name,S,T,units,domain} <: Var{name,S,T,units,domain}`

Defines a diagnostic variable which is allocated and cached per timestep but not integrated over time.

`CryoGrid.DiagnosticVolume`

— Type`DiagnosticVolume`

`Volume`

trait instance for layers with time varying volume where the volume should be treated as a diagnostic state variable.

`CryoGrid.FixedVolume`

— Type`FixedVolume`

`Volume`

trait instance for fixed volume layers. Default for all `Layer`

types.

`CryoGrid.GridOffset`

— TypeBase type for grid alignment, i.e. either "edges" or "cells".

`CryoGrid.Layer`

— Type`Layer`

Abstract base type for all layers.

`CryoGrid.PeriodicBC`

— Type`PeriodicBC{P,S,T1,T2,T3,T4} <: BoundaryProcess{P}`

Periodic boundary condition (of any type/unit) specified by `period`

, `amplitude`

, and `phaseshift`

.

`CryoGrid.Process`

— TypeAbstract base type for all dynamical processes.

`CryoGrid.Prognostic`

— Type`Prognostic{name,S,T,units,domain} <: Var{name,S,T,units,domain}`

Defines a prognostic (time-integrated) state variable.

`CryoGrid.PrognosticVolume`

— Type`PrognosticVolume`

`Volume`

trait instance for layers with time varying volume where the volume should be treated as a prognostic state variable.

`CryoGrid.SubSurface`

— Type`SubSurface <: Layer`

Abstract base type for layers in the stratigraphy, e.g. soil, snow, pond, etc.

`CryoGrid.SubSurfaceProcess`

— Type`SubSurfaceProcess <: Process`

Abstract base type for subsurface processes, i.e. processes that operate at or below the surface, such as heat conduction, water infiltration, etc.

`CryoGrid.Top`

— Type`Top{TProc} <: Layer`

Generic "top" layer that marks the upper boundary of the subsurface grid.

`CryoGrid.Var`

— Type`Var{name,S<:VarDim,T,units,domain}`

Base type for symbolic state variables in the model.

`CryoGrid.VarInitializer`

— Type`VarInitializer{varname}`

Base type for state variable initializers. Initializers of this type are dedicated to a specific state variable with name `varname`

and are run before all other initializers.

`CryoGrid.Volume`

— Method`Volume(::Type{<:Layer})`

Trait for layer types that determines whether its spatial volume is temporally invariant, `FixedVolume`

, or varying with time, `DiagnosticVolume`

or `PrognosticVolume`

.

`CryoGrid.Coupled`

— Method`Coupled(ps::SubSurfaceProcess...)`

Constructs a composite/coupled process from one or more subsurface processes. Alias for `CoupledProcesses(ps...)`

.

`CryoGrid.Coupled`

— Method`Coupled(types::Type{<:Process}...)`

Convenince method which constructs a `CoupledProcesses`

type corresponding to each type in `types`

, e.g:

`Coupled(SnowMassBalance, HeatBalance) = CoupledProcesses{Tuple{T1,T2}} where {T1<:SnowMassBalance, T2<:HeatBalance}`

also equivalent to `Coupled2{<:SnowMassBalance,<:HeatBalance}`

.

`CryoGrid.boundaryflux`

— Method```
boundaryflux(bc::BoundaryProcess, b::Union{Top,Bottom}, p::SubSurfaceProcess, sub::SubSurface, sbc, ssub)
boundaryflux(s::BCKind, bc::BoundaryProcess, b::Union{Top,Bottom}, p::SubSurfaceProcess, sub::SubSurface, sbc, ssub)
```

Computes the flux dH/dt at the boundary layer. Calls boundaryflux(BCKind(B),...) to allow for generic implementations by boundary condition type. Note that this method uses a different argument order convention than `interact!`

. This is intended to faciliate stratigraphy independent implementations of certain boundary conditions (e.g. a simple Dirichlet boundary could be applied in the same manner to both the upper and lower boundary).

`CryoGrid.boundaryvalue`

— Method`boundaryvalue(bc::BoundaryProcess, state)`

Computes the value of the boundary condition specified by `bc`

for the given layer/process combinations. Note that this method uses a different argument order convention than `interact!`

. This is intended to faciliate stratigraphy independent implementations of certain boundary conditions (e.g. a simple Dirichlet boundary could be applied in the same manner to both the upper and lower boundary).

`CryoGrid.caninteract`

— Method```
caninteract(layer1::Layer, layer2::Layer, state1, state2)
caninteract(l1::Layer, ::Process, l2::Layer, ::Process, state1, state2)
```

Returns `true`

if and only if the given layer/process types are able to interact based on the current state. Defaults to checking whether both layers are currently active. This behavior should be overridden by subtypes where necessary.

`CryoGrid.computediagnostic!`

— Method```
computediagnostic!(l::Layer, state)
computediagnostic!(l::Layer, p::Process, state)
```

Updates all diagnostic/non-flux state variables for the given `Layer`

based on the current prognostic state.

`CryoGrid.computefluxes!`

— Method`computefluxes!(l::Layer, p::Process, state)`

Calculates all internal fluxes for a given layer. Note that an instance of `computefluxes!`

must be provided for all non-boundary (subsurface) processes/layers.

`CryoGrid.criterion!`

— Method`criterion!(out::AbstractArray, ev::GridContinuousEvent, ::Layer, ::Process, state)`

Event criterion for on-grid (i.e. multi-valued) continuous events. The condition for each grid cell should be stored in `out`

.

`CryoGrid.criterion`

— Method`criterion(::Event, ::Layer, ::Process, state)`

Event criterion/condition. Should return a `Bool`

for discrete events. For continuous events, this should be a real-valued function where the event is fired at the zeros/roots.

`CryoGrid.diagnosticstep!`

— Method`diagnosticstep!(layer::Layer, state)`

Optionally performs discontinuous/discrete-time updates to the layer state. Should return `true`

if the prognostic state was modified and `false`

otherwise. Defaults to returning `false`

.

`CryoGrid.initialcondition!`

— Method```
initialcondition!(::Layer, state)
initialcondition!(::Layer, ::Process, state)
initialcondition!(::VarInitializer, ::Layer, state)
```

Defines the initial condition for a given `Layer`

and possibly an `initializer`

. `initialcondition!`

should compute initial values into all relevant state variables in `state`

.

`CryoGrid.initialcondition!`

— Method```
initialcondition!(layer1::Layer, layer2::Layer, state1, state2)
initialcondition!(::Layer, ::Process, ::Layer, ::Process, state1, state2)
```

Defines the initial condition for two processes on adjacent layers. `initialcondition!`

should write initial values into all relevant state variables in `state`

.

`CryoGrid.initializer`

— Method```
initializer(varname::Symbol, args...) = initializer(Val{varname}(), args...)
initializer(::Val{varname}, x::Number) => FunctionInitializer w/ constant
initializer(::Val{varname}, f::Function) => FunctionInitializer
initializer(::Val{varname}, profile::Profile, interp=Linear(), extrap=Flat()) => InterpInitializer
```

Convenience constructor for `VarInitializer`

that selects the appropriate initializer type based on the arguments.

`CryoGrid.initializers`

— Method```
initializers(::Layer)
initializers(::Layer, ::Process)
```

Optional method that can be used to provide default initializers for state variables that will be run before user provided ones.

`CryoGrid.interact!`

— Method`interact!(::Layer, ::Process, ::Layer, ::Process, state1, state2)`

Defines a boundary interaction between two processes on adjacent layers. For any interaction, the order of the arguments follows decreasing depth, i.e. the first layer/process is always on top of the second layer/process. This ordering matters and separate dispatches must be provided for interactions in reverse order.

`CryoGrid.interactmaybe!`

— Method```
interactmaybe!(layer1::Layer, layer2::Layer, state1, state2)
interactmaybe!(layer1::Layer, p1::Process, layer2::Layer, p2::Process, state1, state2)
```

Conditionally invokes `interact!`

if and only if `caninteract`

is true.

`CryoGrid.isactive`

— Method`isactive(::Layer, state)`

Returns a boolean whether or not this layer is currently active in the stratigraphy and should interact with other layers. Note that `computediagnostic!`

and `computefluxes!`

are always invoked regardless of the current state of `isactive`

. The default implementation of `isactive`

always returns `true`

.

`CryoGrid.processes`

— Method`processes(l::Layer)`

Fetches the process(es) attached to this layer, if any. Returned value must be of type `Process`

. If the layer has more than one process, they should be combined together with `Coupled(procs...)`

.

`CryoGrid.resetfluxes!`

— Method```
resetfluxes!(layer::Layer, state)
resetfluxes!(layer::Layer, ::Process, state)
```

Resets all flux variables for the given layer/process to zero.

`CryoGrid.timestep`

— Method`timestep(::Layer, ::Process, state)`

Retrieves the recommended timestep for the given `Process`

defined on the given `Layer`

. The default implementation returns `Inf`

which indicates no timestep restriction. The actual chosen timestep will depend on the integrator being used and other user configuration options.

`CryoGrid.timestep`

— Method`timestep(l::Layer, ps::CoupledProcesses{P}, state) where {P}`

Default implementation of `timestep`

for coupled process types. Calls each process in sequence.

`CryoGrid.trigger!`

— Method```
trigger!(::Event, ::Layer, ::Process, state)
trigger!(ev::ContinuousEvent, ::ContinuousTrigger, ::Layer, ::Process, state)
trigger!(ev::GridContinuousEvent, ::ContinuousTrigger, ::Layer, ::Process, state)
```

Event action executed when `criterion`

is met.

`CryoGrid.variables`

— Method```
variables(layer::Layer, process::Process)
variables(::Layer)
variables(::Any)
```

Defines variables for a given `Layer`

, `Process`

, or arbitrary user-defined type. Implementations should return a `Tuple`

of `Var`

s.

`CryoGrid.volumetricfractions`

— Method```
volumetricfractions(::SubSurface, state)
volumetricfractions(::SubSurface, state, i)
```

Get the volumetric fractions of each constituent in the volume (at grid cell `i`

, if specificed). All implementations of `volumetricfractions`

are expected to obey a semi-consistent order in the returned `Tuple`

of fractions; the first three consituents should always be `θw,θi,θa`

, i.e. water, ice, and air, followed by any number of additional constituents which may be defined by the specific layer. There is no feasible way to verify that client code actually obeys this ordering, so be sure to double check your implementation, otherwise this can cause very subtle bugs!